ban-all-sheds said:
There's a red wire going to the earth bar! What is that all about?
And all of that earth sleeving looks green, not green & yellow.
And they changed a CU without testing.
And they didn't leave you a certificate (guess they couldn't if they didn't test).
So a number of wiring regulations have been broken, and I'll bet you'll find that they didn't notify LABC either.
Do you live in a flat or a house? I see no RCD....
BTW - DNO stands for Distribution Network Operator - the company that owns the cables on which the electricity runs, as opposed to the company that makes the electricity or the company that sells it to you or the company that reads the meter. DNOs used to be called RECs - Regional Electricity Companies. Apparently all this fragmentation is good for the customer.
Thanks for that info
Imageshack appears to be playing up a bit today as I've not been able to load the picture up but I have a local copy.
I have no clue why a live is taken down to the earth terminals but it gets a tad worse if you can count up the neutrals and the earths.
There are in total 9 neutral terminals and all are used. That count up includes the terminal from the mains supply. The right most is the busbar from the bottom of the isolator switch to the neutral terminal block.
Now, imho, the earthing terminal block connections are a bit of a mess.
There's been some knitting going on with the tails going to terminals 4 and 5 and terminals 6 and 7. There is bare conductor against insulator on terminals 4 and 5.
The wires going to the earth terminal block are all either green or green and red or red(one only). They didn't do any re-wiring just used the existing cabling coming into the building and the existing circuitry in the building.
Now if you count up the earthed terminals in use there are eight including the curious one doubled up with the red on the third terminal in from the left in that terminal block.
Now the red cable connected up to the earthing block is not of heavy current capability, it's single core and is likely to be for a door bell which I don't have connected up. I believe they may have tied the live cable down to earth to prevent any possiblility of that circuit being unearthed and coming up live by falling into a live connection at any time.
I have no clue of that is correct or reasonable practice and it still leaves me wondering about the neutral for that now unemployed circuit.
Now it depends on how you count up the terminations on the earth block.
If I count all the connected cables then I have 9 but this includes the red one which is presumably from what is meant to be the live side of a circuit somewhere in this flat and which has been tied down to earth.
Discount that red one and there are 8 connected earths plus the one at the second terminal in from the left hand side which is not connected.
I'm not a qualified domestic electrician so some of these comments may be inaccurate.
I understand electromagnetic field theory, magnetism and magnetic materials. I feel quite safe in an HV lab because while there are huge voltages about there is also massive amounts of protection and in the chambers themselves there's a really lovely stick called an earthing bar for added security should one need to attend to the equipment.
I'll post about another query I have with this install in a mo.
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right ... on with the query I have
These are the bits I understand about my CU.
The earth, live and neutral appear to come in from the external supply unit.
In the electricity board meter, there's a cover which can be opened by qualified electrical contractors and under that cover there is a switch so the whole consumer unit can be isolated from the mains supply.
The live and the neutral connect to one side of the isolator unit in the CU.
The earth connects to the earthing terminal block on top left of CU and earths to existing circuits run off that terminal block.
A copper busbar (sleeved in black to the right of the isolator unit) connects the neutral to the neutral terminal block and neutrals for existing circuits run off that.
Live feed to existing circuits run from the top of the MCB's. The live feed from the mains runs along a toothed copper busbar which also connects to the isolator unit thus providing a mains supply that can be isolated at the CU.
Now that all makes sense to me. A problem on a circuit and the MCB trips.
One thing that at first sight doesn't quite make sense is the tying down of an apparently live cable to earth.
Would this be safe? Are there circuits permissible in domestic arrangements which could be such that they have a live and an earth but no neutral? Bear in mind I have a doorbell system installed but it is not in use. There is no doorbell and hasn't been since a new door was fitted some time ago. It's a possible candidate for that live being tied down to earth and in my view that formally makes the circuit safe.
It also implies that if I want to install a door bell I'm going to have to get a 7way CU put in or in fact a 9 way unit with two isolators so that I can dispose of the fuse box that serves the night storage heater and the overnight immersion heater.
Now, during this week a bulb blew in the living room and it tripped the MCB on the lighting circuit. I am happy with that occurring.
When I went to reset the MCB it was the only MCB that had tripped.
All correct and dandy.
Now, I may be misinterpreting the cable layout here.
If you look at the live feed off the 20 A MCB you can quite clearly see that goes off into the flat. There's a number of live feeds running off the 32 A MCB to the right of the 20 A MCB. This 32 A MCB is the sockets circuitry.
Is it ok to have multiple cables running from the live side of the MCB like that?
I suspect there's a link between the 32 A socket MCB and the 6 A lighting MCB. I might be wrong here and that third live feed on the 32 A MCB is running off behind the 6A MCB, it's just very tight, but it looked and felt like a jumper to me and there is a live feed running from the 6A MCB off into the flat. It's difficult to see the tops of those MCB's tho.
Now, if it is a jumper, then what is the purpose of that? It's obviously (?) not bridging the two live feeds, because if it had been doing so and supplying live feed to the lighting circuits from a 32 amp MCB then my lights wouldn't have gone out when the 6 A MCB tripped when the bulb blew.
So I am unsure whether that wire is a jumper or going off into another circuit. Is there any reason there should be jumpers between MCB's on the live side?
Last but not least, if the wiring in the property doesn't pass tests, what do I have to do about it?
Regards
Lesley
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moderator
LesleyB please note 10a